The third year will involve the application of techniques and knowledge gained in the first two years to comparative studies of the polymers previously mentioned. Initial work will continue our efforts to focus upon the variation in amount, type, and conformation of proteins adsorbed onto the various polymers. Analysis of these differences will be correlated with the thrombogenicity of each particular polymer. An attempt will be made to relate the type and conformation of proteins adsorbing onto the polymer and its structure and surface characteristics. This will involve some characterization of the polymer surface and bulk using ESCA, SEM, and ellipsometry. The ex vivo studies will continue, however sheep rather than dogs will be used. This is because of the instability of the canine shunt and the hypercoagulability. The sheep will provide a method of obtainind real time data using fresh blood to which the model protein data analysis can be applied. At this point, using human subjects as was originally proposed would be premature. The complexity and nature of the experiment and data obtained require more extensive experimentation before using human models. Freshly drawn human blood will be used instead. Other studies which will be concurrent with the polymer and sheep work will involve some of the more minor blood proteins and platelet aggregation. Studies such as the induction of the fibrinogen/fibrin conversion using thrombin will be investigated. Spectral analysis of this type of experiment will assist interpretation of the spectral events occurring during blood coagulation.